parsons and s



C. A. PARSONS AND S. S. COOK. METHOD OF FORMING GEAR TEETH.

APPLICATION FILED MAR. 30,1920.

1,401,550, Patented Dec. 27, 1921.

gauze, a. a

UNITED STATES PATENT OFFICE.

COOK, OF WALLSEND, ENGLAND; SAID COOK ASSIGNOB '10 SAID PARSONS.

METHOD OF FORMING GEAR-TEETH.

1,401,550. ori inal application filed May 15, 1am,

To all whom it may concern:

Be it known that we, Cmmnss ALGERNON Parsons and STANLEY SMITH Coon, both subjects of the King of Great Britain and Ireland, residing at Heaton Works Newcastle-upon-Tyne, in the county 0 Nortluunberland, and Turbinia Works, Wallsend-on-Tyne, in the county of Northumberland, England, respectively, have invented certain new and useful Im rovements in a Method of Forming Geareeth, of which the following is a specification.

The present invention relates to the formation of the teeth of gears for power trans mission and has for its object a method of constructing gears with teeth of such form that under the designed conditions of power transmission the transmitted force will be substantially uniformly distributed across each of the faces of interengaging gear pairs.

Gear wheels in which these conditions are fulfilled are described in our Patent No. 1,351,401 filed May 15. 1918, as application Serial Number 234,827 and of which the present application is a division. In these wheels the depth of the slot between consecutive teeth varies across the face of the pinion, being of a greater depth at the end of the pinion nearer to the point at which the driving torque is applied than at the other end.

The accompanying drawing is a diagram showing the correction applied according to the invention.

In the construction of gears for transmission of large powers the teeth are usually formed by the generating process in whic a hob is used having cutting teeth with straight sided flanks and a slight outward taper, as shown in the drawing, so that an increase a in the depth of penetration of the hob into the work causes a decrease 2 v in the thickness of the teeth out on the blank measured at a given distance from the axis of the work, for instance, at the pitch circle.

The present invention consists in machining the teeth of ,ears to a form which gives more uniform distribution of force across the face of the gear for given power conditions, by varying the position of the enerating hob in relation to the axis of t e work as it is fed across the work.

The invention also consists in varying the Specification of Letters I'atent. Patented Dec. 2'7, 1921.

Serial No. 284,857. Divide! and this application filed Karel: 30, 1820. Serial No. 363,867.

radial depth of penetration into the workof the hob eneratmg the gear teeth so that the ar teet formed on the work piece will take tie form requiredto 'vea substantially uniform distribution 0 force er unit width of gear under the designe conditions of transmission. The invention further consists in obtainmg the desired correction by setting the usual straight slide alon which the genersiting hob 1s movedby t e feed screw at a slig 1; angle to the axis of the work piece hem cut, so that the radial depth of penetration of the hob into the work uniformly increases or decreases as it is fed across the face of the ear blank, the test penetration into t 6 work piece oing at the ezlid if the pinion at which the torque is app is The invention also consists in the improved method of forming gear teeth herein described.

In carrying the invention into effect according to one example, I therefore incline the straight slide along which the generating hob in a machine for bobbing gear teeth is moved by the feed screw so that it makes a, lit angle with the axis of the work, or I incline the work so that its axis makes the slight an is with the hob slide, this angle corresponding to the inclination of the curve of deflection due to torsion and bending across the face of the teeth. The set of the slide will usuall be inclined at erent 10s in cut w t e two parts of the doublz helical gear, t e result b to obtain greater penetration into the work piece at one end of the pinion usually the end at which the torque 1s ap lied.

It will be seen that this method of can ing out the correction is extremal simp e and is capable of very accurate a justment and with such a correction almost perfectly uniform distribution is obtained, because in addition to obtaining the close ap roximation to the teeth formation require for 31 fectly uniform distribution, the flexib' 'ty of both sets of teeth and the oil film between their interengaging faces tend to reduce the remaining unevenness of distribution.

In the case I have described the depth of cede bet-ween the halves otthe pinion the decrease will be in opposite directions on the two halves.

Theteeth generated for reduction gearing.

are usually in'volute, the flanks of the generating-hob teeth in longitudinal section being straight-sided. It will be seen, therefore, that in such cases variation in the depth of cnetration will not afiect the exactness o the shape of the teeth but will only affect their thickness.

Having now described our invention what we claim as new and desire to secure by Letters Patent is:--

1. The method of formin gear teeth which consists in machining t e teeth to a form which gives more-uniform distribution of force across the face of the gear for given power conditions, by causing the generatin hob .uniiormly to up roach or reom the axis of the wor: as it is fed across the .work, as set forth.

2, In a method of forming gear teeth,

force er unit-xvi th of gear under the designe conditions of transmission, as set forth.

3. A method of forming gear teeth which consists in setting theusucl straight slide alon which the generating hob is moved by the feed screw at a slight angle to the axis of the workpiece being cut so that the radial depth-of penetration of the hob into the work uniformly increases or decreases as it is fed across the face of the gear blank, the greatest penetration into the workpiece being at the end of the pinion at which the torque is applied, as set forth.

In twtimony whereof we have signed our names to this specification.

CHARLES ALGERNON PARSONS.

STANLEY SMITH COOK. 

